Chapter 1 Fundamentals - Seoul National University · 2018. 1. 30. · Chapter 1 Fundamentals...

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1 /92 Chapter 1 Fundamentals

Transcript of Chapter 1 Fundamentals - Seoul National University · 2018. 1. 30. · Chapter 1 Fundamentals...

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    Chapter 1

    Fundamentals

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    Chapter 1 Fundamentals

    Contents1.1 Scope of Fluid Mechanics

    1.2 Historical Perspective

    1.3 Physical Characteristics of the Fluid State

    1.4 Units and Density

    1.5 Compressibility, Elasticity

    1.6 Viscosity

    1.7 Surface Tension, Capillarity

    1.8 Vapor Pressure

    Objectives

    - Present concept of fluidity

    - Introduce fundamental properties of fluid

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    1.1 Scope of Fluid Mechanics

    • Problems of water supply

    flood prevention

    navigation need to know fluid phenomena

    water power

    irrigation

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    1.2 Historical Perspective

    • d'Alembert (1744)

    "The theory of fluids must necessarily be based upon experiment"

    • d'Alembert paradox theory - ideal, inviscid fluid

    practice - real fluid (viscous)

    • Two schools theoretical group → hydrodynamics

    practical group → hydraulics

    • Navier and Stokes

    → general equations for viscous fluid → equation of motion

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    1.2 Historical Perspective

    [Re] Navier-Stokes equation

    Claude-Louis Navier (1785-1836, French engineer) and George Gabriel

    Stokes (1819-1903, UK mathematician & physicist)

    - one continuity equation + three momentum equations

    - model the weather, ocean currents, water flow in a pipe, the air's flow

    around a wing, and motion of stars inside a galaxy

    - design of aircraft and cars, the study of blood flow, the design of power

    stations, the analysis of pollution,

    - exact solution - one of the seven most important open problems in

    mathematics

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    1.2 Historical Perspective

    • New problems in modern times

    - Dispersion of man's wastes in lakes, rivers, and oceans

    → Environmental Fluid Mechanics (Hydraulics)

    • state: solid

    liquid increasing spacing increasing inter

    fluid gaseous and latitude of molecular cohesive

    plasma particle motion force

    • fluid – continuum → no voids or holes

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    1.3 Physical Characteristics of the Fluid State

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    1.3 Physical Characteristics of the Fluid State

    stressstrain

    solid fluid

    tension

    elastic deformation

    → permanent distortion

    unable to support tension

    (surface tension)

    compressionelastic deformation

    (compressible fluid)

    shear (tangential forces)

    permanent distortion or flo

    w (change shape) to infini

    tesimal shear stress

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    1.3 Physical Characteristics of the Fluid State

    dvdy

    τ µ=

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    1.3 Physical Characteristics of the Fluid State

    stress

    real fluid (viscous fluid)

    ideal fluid

    (non-viscous

    fluid)

    in motion at restat rest and

    in motion

    compression

    (pressure)○ ○ ○

    shear ○ × ×

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    1.3 Physical Characteristics of the Fluid State

    incompressible fluid compressible fluid

    ① Compressibility is of small important. ① Compressibility is predominant.

    ② Liquids and gases may be treated

    similarly.

    ② Behavior of liquids and gases is quite

    dissimilar.

    ③ Fluid problems may be solved with

    the principles of mechanics.

    ③ Thermodynamics and heat transfer

    concepts must be used as well as

    principles of mechanics.

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    1.3 Physical Characteristics of the Fluid State

    • Properties of pressure (compression)

    ① Pressure must be transmitted to solid boundaries normal to those

    boundaries.

    ② At a point, pressure has the same magnitude in all directions.

    → Pressure is a scalar quantity.

    * Fluid does not resist any small shearing stress → "Flow occurs"

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    1.3 Physical Characteristics of the Fluid State

    Weight.W Volγ=

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    1.3 Physical Characteristics of the Fluid State

    0F∑ =

    (a)1 3 sin 0xF p dz p ds θ∑ = − =

    2 3/ 2 cos 0zF p dx gdxdz p dsρ θ∑ = − − =

    [Pf]

    Apply Newton's law for static equilibrium

    (b)

    sindz ds θ=cosdx ds θ=

    1 3 1 3( ) : sin sin 0a p ds p ds p pθ θ∴ − = → =

    Substitute following relations into Eq. (a) & (b)

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    1.3 Physical Characteristics of the Fluid State

    2 3( ) : cos cos cos 02dzb p ds g ds p dsθ ρ θ θ− − =

    2 312

    p p gdzρ∴ = +

    0dz → 2 3p p≈

    1 2 3p p p∴ = = ( 0)dx dz= =

    As then

    at a point

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    1.4 Units and Density

    • SI units - SI system – metric system

    f- Frequency ( ): hertz (HZ = s-1)

    F

    F ma=

    2/ /a v t L t= = 2Lt− /v L t= 1Lt−

    21kg m/s 1N( )F Newton∴ → ⋅ =

    • Force,

    → introduce Newton's 2nd law of motion

    Force = mass × acceleration

    (m/s2)

    (m/s)

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    1.4 Units and Density

    Dimension SI unit English system (FSS)

    Length (L) metre (m) feet (ft)

    Mass (M) kilogram (kg) slug (-)

    Time (t) second (s) second (s)

    Temp. (T) kelvin (K) degree Rankine (°R)

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    1.4 Units and Density

    E2 2kg m /s ( )E FL J Joule= → ⋅ =

    P2 3/ / kg m sP E t J s= → = ⋅

    p ,σ τ2 2/ N/m Pa (pascal) kg/m sp F A= → = = ⋅

    T

    • Energy, (work)

    • Power,

    • Pressure, ; Stress,

    • Temperature, : degree Celsius (°C)

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    1.4 Units and Density

    ρ

    3kg/mMV

    ρ = →

    • Density,

    = mass per unit volume

    ~ depends on the number of molecules per unit of volume

    ~ decreases with increasing temperature

    γ

    3 2 2N/m kg/m sWV

    γ = → = ⋅

    • Specific weight (weight density),

    = weight (force) per unit volume

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    1.4 Units and Density

    (1.1)

    W Mg=g

    gγ ρ∴ =

    [Re](Newton’s 2nd law of motion)

    = acceleration due to gravity

    1/ ρ• Specific volume=volume per unit mass=

    • Specific gravity, s.g. , ~ r. d. (relative density)

    = ratio of density of a substance to the density of water at a specified

    temperature and pressure

    . . f fw w

    s gρ γρ γ

    = =

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    1.4 Units and Density

    [Re] s.g. of sea water = 1.03

    s.g. of soil = 2.65

    s.g. of mercury = 13.6

    ( )F ( )M• Advantage of SI system and English FSS system

    ① It distinguishes between force and mass .

    ② It has no ambiguous definitions.

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    1.4 Units and Density

    SI English system

    1,000 kg/m3 1.94 slugs/ft3

    9,806 N/m3 62.4 lb/ft3

    9.81 m/s2 32.2 ft/s2

    ρ

    γ

    g

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    1.4 Units and Density

    α

    β,γ Γ

    ,δ ∆εζη

    ,θ Θ

    ι

    • Greek Alphabet

    Alpha angle

    Beta [beitə] angle

    Gamma specific weight, circulation

    Delta thickness of boundary layer

    Epsilon eddy viscosity, height of surface roughness

    Zeta

    Eta

    Theta

    Iota [aioutə]

    Kappa [kæpə]κ

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    1.4 Units and Density

    ,λ Λ

    µ

    νξοπ

    ρ

    ,σ ∑

    τ

    Lambda

    Mu [mju:] dynamic viscosity

    Nu kinematic viscosity

    Xi [gzai, ksai] vorticity

    Omicron

    Pi [pai]

    Rho mass density

    Sigma Sigma Xi, Scientific Research Society, 1886

    honor society for scientists & engineers

    Tau shear

    Upsilon,υ ϒ

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    1.4 Units and Density

    ,ϕ Φ

    χ

    ,ψ Ψ

    ,ω Ω

    Phi [fai] Phi Beta Kappa

    Chi [kai]

    Psi [psai, sai] stream function

    Omega angular velocity

    • Prefixes

    E exa 1018

    P peta 1015

    T tera 1012

    G giga 109

    M mega 106

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    1.4 Units and Density

    µ

    M mega 106

    k kilo 103

    h hecto 102

    da deca 101

    d deci 10-1

    c centi 10-2

    m milli 10-3

    micro 10-6

    n nano 10-9

    p pico 10-12

    f femto 10-15

    a atto 10-18

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    1.5 Compressibility, Elasticity

    • Elastic behavior to compression

    • Compressibility ≡ change in volume due to change in pressure

    solid - modulus of elasticity, E (N/m2)

    fluid - bulk modulus

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    1.5 Compressibility, Elasticity

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    1.5 Compressibility, Elasticity

    1

    dVdpV

    ∝1

    dVdp EV

    → = −

    1

    1

    ( , )dp dpE V const fn p TdV dVV

    = − = − ≠ = → p E↑ → ↑

    1

    1 1dVCE V dp

    = = −

    • Stress-strain curve (E↑, difficult to compress)

    = modulus of compressibility (m2/N)

    Minus means that increase in

    pressure causes decrease in

    volume

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    1.5 Compressibility, Elasticity

    , 1E C= ∞ ρ

    [Re] large E/small C → less compressible

    • incompressible fluid (inelastic):

    → constant density =const.

    ~ water

    • compressible fluid

    → changes in density → variable density

    ~ gas

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    1.5 Compressibility, Elasticity

    Pressure

    106 N/m2

    Temperature, °C

    0° 20° 50° 100° 150°

    0.1 1950 2130 2210 2050

    10.0 2000 2200 2280 2130 1650

    30.0 2110 2320 2410 2250 1800

    100.0 2530 2730 2840 2700 2330

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    1.5 Compressibility, Elasticity

    E

    E

    - increases as pressure increases.

    - is maximum at about 50 °C.

    → The water has minimum compressibility at about 50 °C.

    1dpE VdV

    = −

    1

    V pV E∆ ∆

    ≈ −

    2 1 2 1

    1

    V V p pV E− −

    ≈ −

    • For the case of a fixed mass of liquid at constant temperature

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    1.5 Compressibility, Elasticity

    Compressibility Modulus of Elasticity, E (kPa)

    steel 1/80 of water water 2,170,500

    mercury 1/12.5 of water sea water 2,300,000

    nitric acid 6 of water mercury 26,201,000

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    1.5 Compressibility, Elasticity

    62,200 10 PaE = ×6

    2 1 7 10 Pap p= + ×

    2 1 2 1

    1

    0.0032V V p pV E− −

    ∴ ≈ − = −

    2 1(1 0.0032)V V∴ = −

    0.3%V∆ ≈

    [Ex] For water; @ 20˚C

    decrease

    → water is incompressible

    63

    7 10 Pa 70101.3 10 Pap×∆ = ≈

    ×기압

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    1.6 Viscosity

    [Re] From Wikipedia

    Viscosity is a measure of the resistance of a fluid which is being

    deformed by either shear stress or tensile stress.

    Viscosity ~ "thickness" or "internal friction"

    ▪ water ~ "thin", having a lower viscosity

    ▪ honey ~ "thick", having a higher viscosity

    The less viscous the fluid is, the greater its ease of movement (fluidity).

    Viscosity describes a fluid's internal resistance to flow and may be

    thought of as a measure of fluid friction.

    dvdy

    τ µ=

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    1.6 Viscosity

    For example, high-viscosity felsic magma will create a tall, steep

    stratovolcano, because it cannot flow far before it cools, while low-

    viscosity mafic lava will create a wide, shallow-sloped shield volcano.

    All real fluids (except superfluids) have some resistance to stress and

    therefore are viscous, but a fluid which has no resistance to shear stress

    is known as an ideal fluid or inviscid fluid.

    [Re] super fluid – a fluid having frictionless flow, and other unusual

    properties

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    1.6 Viscosity

    • Two types of fluid motion (real fluid)

    1) laminar flow:

    - viscosity plays a dominant role

    - fluid elements or particles slide over each other in layers (laminar)

    - molecular diffusion

    [Ex] flow in a very small tube, a very thin flow over the pavement, flow in

    the laminar flow table

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    1.6 Viscosity

    Re Vdν

    =

    where V = flow velocity; d = characteristic length; n = kinematic viscosity

    Diameter of pipe,Depth of stream

    2) turbulent flow:

    - random or chaotic motion, eddies of various sizes are seen

    - common in nature (streams, rivers, pipes)

    - large scale mixing between the layers

    • Reynolds number

    [Ex] flows in the water supply pipe, flows in the storm sewer pipe, flows in

    the and canals and streams

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    1.6 Viscosity

    • Reynolds experiments

    laminar flow: Re < 2,100

    transition: 2,100 4,000

    The same fluid withdifferent velocity

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    1.6 Viscosity

    Spiralsecondaryflow

    Secondaryflow

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    1.6 Viscosity

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    1.6 Viscosity

    cubestreamline

    source

    sink

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    1.6 Viscosity

    Smoothsurface

    Eddyingmotion

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    1.6 Viscosity

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    1.6 Viscosity

    Symmetric shape,No separation

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    1.6 Viscosity

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    1.6 Viscosity

    Separation, eddyformation

    Growthof eddy

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    1.6 Viscosity

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    1.6 Viscosity

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    1.6 Viscosity

    • laminar flow

    2 1d d dvdt dv dtdy dy dy−

    = = = yxdGdyζτ =

    2 2 1 1

    2 1 2 1

    ;( )

    d v dt d v dtd d v v dt

    = =− = −

    • strain = relative displacement [Cf] solid mechanics

    [Re] total angular displacement

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    1.6 Viscosity

    no velocity at theboundary (no slip)

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    1.6 Viscosity

    τ• Experiment has shown that, in many fluids, shearing (frictional) stress

    per unit of contact area, is proportional to the time rate of relative

    strain.

    /dv dvdt dtdy dy

    τ∴ ∝ =

    dvdy

    τ µ= →

    (velocity gradient)

    Newton’s equation of viscosity (1.2)

    µwhere = coefficient of viscosity

    = dynamic (absolute) viscosity

    Large → sticky, difficult to flowµ

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    1.6 Viscosity

    • viscosity = measure of fluid's resistance to shear or angular

    deformation

    = internal resistance of a fluid to motion (fluidity)

    [Re] Friction forces result from

    - cohesion for liquid

    - momentum interchange between molecules for gas

    [Re] angular deformation due to tangential stress

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    1.6 Viscosity

    dy

    x

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    1.6 Viscosity

    du duu y t u t y tdy dy

    = + ∆ ∆ − ∆ = ∆ ∆

    /du duy t y tdy dy

    = ∆ ∆ ∆ = ∆

    • rate of angular deformation

    (i) displacement of AB relative to CD

    (ii) angular displacement of AC

    (iii) time rate of angular deformation

    /du dut tdy dy

    = ∆ ∆ =

    dvdy

    τ µ=

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    1.6 Viscosity

    µ• dynamic viscosity,

    /F Aτ =

    [ ] 2 2 1 2 2/ kg/(m s ) PaMLT L ML Tτ − − − = = ⋅ = 1

    1dv LT Tdy L

    −− = =

    [ ]1 2

    1 1 21/ kg/m s N s / m Pa s

    dv ML T ML Tdy T

    µ τ− −

    − −−

    ∴ = = = = ⋅ = ⋅ = ⋅

    11 ( ) 10 Pa spoises Poiseuille −⇒ = ⋅

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    1.6 Viscosity

    ν• kinematic viscosity,µνρ

    =

    [ ]1 1

    2 1 23 m /s

    ML T L TML

    ν− −

    −−

    = = =

    (1.3)

    1 m2/s = 104 stokes =106 centistokes

    ,τ µ

    τ τ

    • Remarks on Eq. (1.2)

    ① are independent of pressure. [Cf] friction between two moving

    solids

    ② Shear stress (even smallest ) will cause flow (velocity gradient).

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    1.6 Viscosity

    0 0dvdy

    τ= → = µregardless of

    ③ Shearing stress in viscous fluids at rest will be zero.

    dvdy

    ≠ ∞ τ→ ≠ ∞④ At solid boundary, ( (no infinite shear))→ Infinite shearing stress between fluid and solid is not possible.

    ⑤ Eq. 1.2 is limited to laminar (non-turbulent) fluid motion in which

    viscous action is predominant.

    [Cf] turbulent flow

    εε µ

    dvdy

    τ ε=

    where = eddy viscosity

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    1.6 Viscosity

    ⑥ Velocity at a solid boundary is zero.

    → No slip condition (continuum assumption)

    • Newtonian and non-Newtonian fluids

    i) Newtonian fluid ~ water

    ii) Non-Newtonian fluid ~ plastic, blood, suspensions, paints, polymer

    solutions → rheology

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    1.6 Viscosity

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    1.6 Viscosity

    1dvdy

    τ τ µ− =

    ndvKdy

    τ

    =

    1n >

    1n <

    • Non-Newtonian fluid

    1) plastic, = threshold

    2) Shear-thickening fluid

    Shear-thinning fluid

    • Couette flow: laminar flow in which the shear stress is constant

    thin fluid film between two large flat plates

    thin fluid film between the surfaces of coaxial cylindersdv Vdy h

    =

    Vh

    τ µ∴ =

    ~ linear velocity gradient

    ~ constant

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    1.6 Viscosity

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    1.6 Viscosity

    ( ) dvdy

    τ µ ε= +

    ε

    • Turbulent flow

    = eddy viscosity = viscosity due to turbulent factor

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    1.6 Viscosity

    gas liquid

    main cause of

    viscosity

    exchange of molecule's momentum →

    interchange of molecules between

    the fluid layers of different velocities

    intermolecular cohesion

    effect of

    temperature

    variation

    temp↑ → molecular activity↑

    → viscosity↑ → shearing stress↑

    temp↑ → cohesion↓

    → viscosity↓ → shear stress↓

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    1.6 Viscosity

    Two layers tendto stick togetheras if there is some viscosity between two.

    [Re] Exchange of momentum

    fast-speed layer (FSL)

    molecules from FSL speed up molecules in LSL

    molecules from LSL slow down molecules in FSL

    low-speed layer (LSL)

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    1.6 Viscosity

    mv

    1) exchange of momentum : exchange momentum in either direction from

    high to low or from low to high momentum due to random motion of

    molecules

    2) transport of momentum : transport of momentum from layers of high

    mome

    (high velocity, ) to layers of low momentum

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    1.7 Surface Tension, Capillarity

    nf

    σ

    • surface tension

    - occur when the liquid surfaces are in contact with another fluid (air) or

    solid

    - (relative sizes of intermolecular cohesive and adhesive forces to

    another body)

    - as temp↑ → cohesion↓ → ↓ ☞ Table A2.4b, p. 694

    • some important engineering problems related to surface tension

    - capillary rise of liquids in narrow spaces

    - mechanics of bubble formation

    - formation of liquid drops

    - small models of larger prototype → dam, river model

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    1.7 Surface Tension, Capillarity

    σ /F L• surface tension, ( , N/m)- force per unit length

    - force attracting molecules away from liquid

    0F∑ = , , ,a b c d

    0( ) 2 sin 2 sinip p dxdy dy dxσ α σ β− = +

    Consider static equilibrium

    (forces normal to the element )

    where pi = pressure inside the curvature; po = pressure inside the

    curvature1

    sin ,2dxR

    α =2

    sin2dyR

    β = [ ]12( sin )dx R α=

    01 2

    1 1ip p R R

    σ

    ∴ − = +

    (1.4)

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    1.7 Surface Tension, Capillarity

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    1.7 Surface Tension, Capillarity

    • Cylindrical capillary tube

    - due to both cohesion and adhesion

    cohesion < adhesion → rise (water)

    cohesion > adhesion → depression (mercury)

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    1.7 Surface Tension, Capillarity

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    1.7 Surface Tension, Capillarity

    1 2R R R= = ≈

    0p hγ= −

    0ip =

    For a small tube, given conditions are as follows

    (liquid surface section of sphere) ← Ch. 2

    (hydrostatic pressure)

    (atmospheric)

    01 2

    1 1ip p R R

    σ

    − = + 2h

    Rγ σ∴ =

    Substitute above conditions into Eq. 1.15: (1.4)

    cosr R θ=2 2 cos

    / cosh

    r rσ θγ σ

    θ∴ = =

    2 coshr

    σ θγ

    =

    By the way,

    (1.5)

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    1.7 Surface Tension, Capillarity

    h r hθr ≤

    in which = capillary rise → ↑ → ↓

    = angle of contact

    = radius of tube 2.5 mm for spherical form

    12r > h[Ex] water and mercury → Fig. 1.11

    If mm, is negligible for water.

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    1.7 Surface Tension, Capillarity

    cohesion > adhesion

    → depression

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    1.7 Surface Tension, Capillarity

    • Pressure measurement using tubes in hydraulic experiments

    → Ch.2 manometer

    ~ capillarity problems can be avoided entirely by providing tubes large

    enough to render the capillarity correction negligible.

    • Fomation of curved surface, droplet

    - At free liquid surface contacting the air, cohesive forces at the outer

    layer are not balanced by a layer above.

    →The surface molecules are pulled tightly to the lower layer.

    →Free surface is curved.

    [Ex] Surface tension force supports small loads (water strider).

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    1.7 Surface Tension, Capillarity

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    1.7 Surface Tension, Capillarity

    0 1.0ip p− =

    0.0728σ =At 20°C, N/m ← App. 2

    [IP 1.10] For a droplet of water (20 °C), find diameter of droplet

    Given: kPa

    01 2

    1 1 2ip p R R R

    σσ

    − = + =

    ∴1R⋅

    0.000146m 0.146mmR∴ = = 0.292d→ =

    [Sol]

    (1.4)

    1×103 N/m2 = 2(0.0728)

    mm

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    1.7 Surface Tension, Capillarity

    [IP 1.11] Find height of capillary rise in a clean glass tube of 1 mm

    diameter if the water temperature is 10°C or 90°C.

    [Sol]

    From App. 2 Table A 2.4b;

    σ γ

    σ γ@ 10°C =0.0742 N/m, = 9.804 kN/m3

    @ 90°C =0.0608 N/m, = 9.466 kN/m3

  • 79/92

    1.7 Surface Tension, Capillarity

    Use Eq. 1.16

    For water, 0θ =

    2 coshr

    σ θγ

    =

    1̀02(0.0742)(1) 0.030m=30mm

    9804(0.0005)h∴ = =

    902(0.0608)(1) 0.026m=26mm

    9466(0.0005)h = =

    (1.5)

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    1.8 Vapor Pressure

    • vapor pressure = partial pressure exerted by ejected molecules of liquid

    → Table A2.1 and A2.4b

    • liquids ~ tend to vaporize or evaporate due to molecular thermal

    vibrations (molecular activity)

    → change from liquid to gaseous phase

    temperature↑ → molecular activity↑ → vaporization↑ → vapor pressure↑

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    1.8 Vapor Pressure

    55.2 kPavp =2.34 kPavp =

    0.00017 kPavp =

    • volatile liquids:

    ~ easy to vaporize → high vapor pressure

    gasoline: at 20 °C

    water: at 20 °C

    mercury: at 15.6 °C

    • mercury : low vapor pressure and high density = difficult to vaporize

    → suitable for pressure-measuring devices

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    1.8 Vapor Pressure

    In the interior and/or boundariesof a liquid system

    High velocity region

    • Cavitation: App. 7 (p. 672)

    In a flow fluid wherever the local pressure falls to the vapor pressure of

    the liquid, local vaporization occurs.

    → Cavities are formed in the low pressure regions.

    → The cavity contains a swirling mass of droplets and vapor.

    → Cavities are swept downstream into a region of high pressure.

    → Then, cavities are collapses suddenly.

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    1.8 Vapor Pressure

    → surrounding liquid rush into the void together

    → it causes erosion (pitting) of solid boundary surfaces in machines, and

    vibration

    → boundary wall receives a blow as from a tiny hammer

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    1.8 Vapor Pressure

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    1.8 Vapor Pressure

    • Prevention of cavitation

    ~ cavitation is of great importance in the design of high-speed hydraulic

    machinery such as

    turbines, pumps, in the overflow and underflow structures of high dams,

    and in high-

    speed motion of underwater bodies (submarines, hydrofoils).

    → design improved forms of boundary surfaces

    → predict and control the exact nature of cavitation → set limits

    Bodycavitation

  • 86/92

    1.8 Vapor Pressure

  • 87/92

    1.8 Vapor Pressure

    atm vp p≤

    • Boiling:

    = rapid rate of vaporization caused by an increase in temperature

    = formation of vapor bubbles throughout the fluid mass

    ~ occur (whatever the temperature) when the external absolute pressure

    imposed on the

    liquid is equal to or less than the vapor pressure of the liquid

    ~ boiling point = f (imposed pressure, temp.)

    → boiling occurs

  • 88/92

    1.8 Vapor Pressure

    altitude

    (El. m)

    Temp.

    (°C)

    (kPa),

    absolute

    (kPa),

    absolute

    boiling point

    (°C)remark

    m.s.l. 100 101.3 101.3 100

    12,000 60 19.9 19.4 60 undercooked

    vp atmp

    Table A2.4b

    Table A2.5b

  • 89/92

    1.8 Vapor Pressure

    vp• Evaporation: When the space surrounding the liquid is too large, the

    liquid continues to

    vaporize until the liquid is gone and only vapor remains at a pressure

    less than or equal.

    [IP 1.12] For a vertical cylinder of diameter 300 mm, find min. force that

    will cause the water boil.

  • 90/92

    1.8 Vapor Pressure

    Patm=100 kpa

    Water @ 70˚C

  • 91/92

    1.8 Vapor Pressure

    vp

    'vp p≤

    ' 100 31.16FpA

    ∴ = − =

    2(0.3)(100 31.16) 4.87 kN4

    F π∴ = − =

    [Sol] From Table A2.4b; =31.16 kPa at 70 °C

    =31.16, For water to boil;

  • 92/92

    1.8 Vapor Pressure

    Homework Assignment # 1

    Due: 1 week from today

    Prob. 1.2

    Prob. 1.10

    Prob. 1.27

    Prob. 1.46

    Prob. 1.49

    Prob. 1.58

    Prob. 1.69

    Prob. 1.72

    Prob. 1.82

    Chapter 1Chapter 1 Fundamentals1.1 Scope of Fluid Mechanics��1.2 Historical Perspective��1.2 Historical Perspective��1.2 Historical Perspective��1.3 Physical Characteristics of the Fluid State��1.3 Physical Characteristics of the Fluid State��1.3 Physical Characteristics of the Fluid State��1.3 Physical Characteristics of the Fluid State��1.3 Physical Characteristics of the Fluid State��1.3 Physical Characteristics of the Fluid State��1.3 Physical Characteristics of the Fluid State��1.3 Physical Characteristics of the Fluid State��1.3 Physical Characteristics of the Fluid State��1.4 Units and Density��1.4 Units and Density��1.4 Units and Density��1.4 Units and Density��1.4 Units and Density��1.4 Units and Density��1.4 Units and Density��1.4 Units and Density��1.4 Units and Density��1.4 Units and Density��1.4 Units and Density��1.5 Compressibility, Elasticity��1.5 Compressibility, Elasticity��1.5 Compressibility, Elasticity��1.5 Compressibility, Elasticity��1.5 Compressibility, Elasticity��1.5 Compressibility, Elasticity��1.5 Compressibility, Elasticity��1.5 Compressibility, Elasticity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.6 Viscosity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.7 Surface Tension, Capillarity��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��1.8 Vapor Pressure��